1. Field of the Invention
This invention relates to a container inspection process for detecting the presence of contaminants in plastic containers. More specifically, this invention relates to identifying plastic containers which have organic compounds present on or absorbed into the walls of such containers by analyzing the vapors therein.
2. Description of the Prior Art
Plastic containers, such as polyethylene terephthalate (PET) bottles, have long been used for the packaging of carbonated and noncarbonated beverages. Typically, these containers are only used once and then discarded. However, in certain geographic areas, such as central Europe, multiple use containers dominate the beverage container industry. In such areas, the opportunity to use plastic containers is primarily for multiple use containers.
While plastic containers have perceived advantages over glass containers, such as weight and convenience, a perceived disadvantage of reusing plastic containers has been the potential for absorption of certain contaminants into the container walls after the rare occurrence of container misuse by a consumer. These absorbed contaminants have the potential to be desorbed back into the beverage when the container is refilled. Thus, the present process provides a means of identifying certain contaminants that are present on the container walls or that have been absorbed into the container walls.
Generally, conventional container inspection systems were developed for glass containers and were not concerned with absorption of contaminants into the container walls. These conventional systems are typically used for detecting the presence of solid particles or for the detection of contaminants in product-filled containers. For example, see U.S. Pat. No. 4,376,951 to Miyazawa, U.S. Pat. No. 4,551,627 to Wriech, U.S. Pat. No. 4,221,961 to Peyton, U.S. Pat. No. 4,087,184 to Knapp et al., U.S. Pat. No. 4,083,691 to McCormack et al, U.S. Pat. No. 3,966,332 to Knapp et al, and U.S. Pat. No. 4,459,023 to Wriech et al.
However, the present invention provides a novel process for detecting contaminants which are present on or have been absorbed into the walls of plastic containers. Moreover, this invention provides a process which is commercially viable for inspecting and reusing plastic containers in the beverage industry.